Taylor Swift & Calvin Harris mixed business with pleasure, and it backfired

Christina is a reporter based in Boise, Idaho. She's a veteran vegetarian, a political junkie and a huge grammar snob. On the weekends, she can usually be found binging on Netflix, playing the piano or petting her cats, Daisy and Dandelion.

The couple who 'works together, stays together' didn't work out for Taylor Swift & Calvin Harris

We may never know exactly what went on behind the scenes leading up to Taylor Swift's breakup with Calvin Harris — undoubtedly one of the most devastating celebrity splits of all time. But does a new revelation about their business relationship provide clues into what caused the sudden end of their personal one?

Swift's rep has finally confirmed that Harris' hit single recorded with Rihanna, "This Is What You Came For," was actually written by Swift under the pseudonym Nils Sjöberg. The confirmation came very soon after TMZ reported that Swift had written the song.

Swift "wrote the song, sat down at a piano and did a demo into her iPhone," and sent the demo to her then-boyfriend Harris, TMZ writes. The two soon got together to record a full demo, but agreed to keep their collaboration secret at the time.

Then, while Harris was promoting the song, he did an interview with Ryan Seacrest, during which he was asked whether he would ever collaborate with Swift.

"You know, we haven't even spoken about it. I can't see it happening though," Harris answered.

Ouch.

Swift was reportedly — and understandably — hurt by Harris' comment; he made it while he was promoting the song she wrote for him, for crying out loud. Could this have been at least part of the reason the couple decided to call it quits after dating for more than a year?

According to Harris, whatever Swift felt about the comment was enough for her and her team to work to make him look like the bad guy. He tweeted a long rant saying, "I wrote the music, produced the song, arranged it and cut the vocals though. And initially she wanted it kept secret, hence the pseudonym."

He tweeted: "I figure if you're happy in your new relationship you should focus on that instead of trying to tear your ex bf down for something to do. I know you're off tour and you need someone new to try and bury like Katy etc. but I'm not that guy, sorry. I won't allow it."

Double ouch.

Regardless of the reasoning behind their breakup, or the reason the songwriting drama is public now, Harris and Swift seem to be moving on. Harris is releasing more new music, and Swift has been seen globetrotting with her new boyfriend, Tom Hiddleston.